순 AI 과 순 Cu 의 진동 특성에 미치는 시편 크기의 영향

장충근,권혁무,박헌범 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.4

The vibration properties of the pure Al plate and pure Cu plate, 12 ㎜ wide and 164∼254 ㎜ long, were investigated by cantilever beam and RFDA to get the following results. (1) The results by cantilever beam method and RFDA show that the resonance frequency decreases as the specimen length increases or the thickness decreases. (2) When measuring the vibration by the cantilever beam method, the vibration damping coefficients are stable at the specimen with 184 ㎜ or higher length. (3) When measuring the vibration damping coefficient by the cantilever beam method, the mean vibration damping ratio of Al specimen 1.6∼0.8 ㎜ thick is 3.1×10^(-2) and 4.0×10^(-2) in Cu specimen of 2.0∼1.2 ㎜ (4) When measuring the vibration damping properties by the RFDA, vibration damping coefficients are similar regardless of the length and thickness of a specimen and the mean vibration damping ratios of Al and Cu were 2.1×10^(-2) and 2.7×10^(-2), respectively. (5) As a result of (3) and (4), The relationship, between the vibration damping ratio measured by the cantilever beam method and it by the RFDA was founded as g_s=(δ_o/δ_r)×(1/1.5).

Tropane Spirohydantoin들의 합성 및 구조분석

정대일,이도훈,송주현,이용균,최순규,박유미,한정태 동아대학교 환경문제연구소 2006 硏究報告 Vol.28 No.1

The tropane ring system is an important substructure in a number of natural products and synthetic compounds of biological and medicinal importance. As a result of the significance of the tropane ring system, the purpose of this study is the synthesis of anticonvulsant compounds of new s tructure anticipated anticonvulsant activity. After we first synthesized the various N-substituted nortropinone derivatives, we prepared new nortropane alkaloids and nortropinone derivatives. Substantially, we tried several experiments to optimize reaction condition. The tropane spirohydantoins 17, 18, 19, 20, 21 were respectively synthesized by the treatment of corresponding N-substituted nortropinone with potassium cyanide and ammonium carbonate.

조사료의 종류가 홀스타인 송아지 유선의 발달 , 반추위 돌기 및 성장률에 미치는 영향

조광근,최윤재,박영우,윤연화,한영근,윤상기,권웅기 한국영양사료학회 1999 韓國營養飼料學會誌 Vol.23 No.6

본 연구는 홀스타인 송아지에 대한 세 종류의 조사료가 유선조직, 반추위 유두, 번식성적 및 성장률에 미치는 영향을 조사하기 위하여 실시하였다. 출생 후 4일된 송아지(42.9±0.9㎏) 24두를 무작위로 선발하여 출생 후 4∼44일까지 전유를 급여하다가 45일에 그룹 1은 볏짚, 그룹 2는 오차드 그래스, 그룹 3은 알괄파를 급여하였다. 또한 유선조직과 반추위의 발달을 측정하기 위하여 3, 9, 18개월령에 도달하였을 때 각 처리구의 송아지를 1마리씩 도살하였다. 알팔파를 급여한 그룹 3은 다른 처리구에 비하여 중체율이 높았으며, 그룹 2는 영양소 이용률과 번식성적이 높은 경향을 나타내었다. 반추위의 무게는 3개월령 도달시에는 그룹 3이 가장 무거웠으나, 9개월과 18개월령 도달시에는 그룹 2에서 가장 무거운 것으로 나타났다. 반추위의 유두 수는 유두의 성장과 함께 일반적으로 감소하는 경향을 나타내어 유두의 길이와 유두 수와는 서로 상대적인 관계를 나타내었다. 유선의 기능적 활성을 나타내는 RNA/DNA 함량은 3개월 시에는 그룹 3이 가장 낮은 경향을 보였으나 9, 18개월 시에는 반대로 가장 높은 경향으로 나타났으며, 유선세포의 크기를 나타내는 protein/DNA 함량은 18개월 시에 그룹 2가 가장 높은 경향을 보였다. 결론적으로 본 연구에서 볏짚은 반추위의 초기 발달을 촉진하고 알팔파와 오차드그래스는 성장과 번식성적을 증가시키며 또한 초기에 유선의 발달을 촉진시키는 것으로 나타났다. Twenty-four Holstein calves were used to evaluate the effects of three different forages on growth and reproductive performances, and ruminal papillary and mammary developments. Four-day-old Holstein calves weighing 42.9±0.9 ㎏ were randomly assigned to three forage groups of rice straw (group 1), orchard grass hay (group 2), and alfalfa (group 3). All calves received whole milk from day 4 through day 44. At 45 days of age, the animals were assigned at random to one of the three dietary treatments. When calves reached the ages of 3, 9, and 18 months, one calf in each group was sacrifced for evaluation of ruminal and mammary tissue developments. Calves of group 3 gained more body weight than those of other groups, while group 2 showed an effective nutrient utilization and reproduction performance. At 3 months, the stomach weight of group 3 was the highest, however, group 2 provided the highest stomach weight at 9 and 18 months. A remarkable reduction in papillae number was observed in the rumens of all 3- to 9-month-old heifers. A decrease in number of these papillae was observed in all groups exhibiting papillary growth. There was a reciprocal relationship between the number and the length of ruminal papillae. Among the 3-month-old calves, the functional activity (RNAI DNA contents) of the mammary glands of group 3 was lower than those of other groups, whereas the trend was opposite for 9- and 18-month-old heifers. The size of mammary cell (protein / DNA contents) was the greatest for group 2 at 18 months of age. The results suggest that rice straw stimulated earlier development of rumen. Alfalfa and orchard grass improved the growth, reproduction performance, and earlier development of mammary glands.

TiNi 가 섬유가 TiNi (Co)/Al 형상기억복합재료의 피로균열전파에 미치는 영향

박영철,윤두표,김순국,이준희,이규창 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.5

In this paper, TiNiCo/Al shape memory composites were fabricated by powder metallurgy method. TiNi and TiNiCo were used as fiber for reinforcement. To investigate the fatigue crack propagation behavior due to the compressive residual stress which exists in the composites, fatigue test was performed at room temperature and above the inverse transformation temperature A_f of TiNi and TiNiCo shape memory alloy. Results are as follows; At 363 K, both composites have lower fatigue crack propagation rate than pure matrix in the same ΔK area and the fatigue crack propagation of TiNi/Al composite is lower than that of TiNiCo/Al composite.

쇼크 업소버의 소음 발생 요인과 진동감쇠 특성에 관한 연구

박태원,신귀수,이기형,김경모,정인성 한국산업안전학회 1998 한국안전학회지 Vol.13 No.4

Shock absorber has a great influence on the performance of the vehicle(ride comfort, manipulation, noise, vibration, turning, stability). Therefore, in this study we consider theoretically about general damper, variable damping oil damper, the control of vehicle Characteristics for the suspension, and undesirable phenomenon. And we measured the vibration/noise characteristics of shack absorber for the real car experimentation, strain change, and noise characteristics of shock absorber using experimental equipment. The study of domestic company and research institute on the vehicle shock absorber is active, but that of basis is not. So we think that they should be accomplished actively. Therefore, this paper will develop theoretical system on the vibration/noise characteristics of shock absorber by theoretical consideration and experimental result analysis of dynamic characteristics of shock absorber that were accomplished in this study. Then we will use it as the optimistic design data for shock absorber development.

LDPE 에서 발생된 전기트리에 수반된 내부 부분방전 펄스 해석

박영국,임기조,강성화,권순석,신태수 한국산업안전학회 1999 한국안전학회지 Vol.14 No.1

전력용 케이블은 전선로의 지중화 추세에 따라 사용이 증가하고 있다. 케이블 절연체의 경우 장기간의 전압인가에 의해 열화 및 절연파괴 된다. 전력용 케이블의 절연파괴시 발생하는 사회/경제적 문제는 매우 심각한 것으로 알려져 있다. 절연체의 열화에 영향을 주는 요인은 매우 복잡하지만 그중에서도 전기트리 열화에 의한 파괴는 비교적 두꺼운 고체 유전체인 경우에 절연파괴 사고의 주된 원인이 되고 있다. 전기트리의 개시나 진전시 부분방전이 발생하므로 부분방전의 검출에 의해 전기트리의 발생 및 진전 양상을 관측할 수 있고 부분방전의 해석에 의해 절연재료의 잔여 수명을 예측할 수 있다. 본 논문에서는 고전압 전력용 케이블 절연재로써 광범위하게 사용되고 있는 저밀도 폴리에틸랜 시편에서의 전기트리 진전 양상을 비파괴 진단 기법에 의하여 검출하고자 내분 부분방전을 관측/해석하였다. The correlation between propagation of electrical tree and internal partial discharges is discussed. We use specimens with needle-plane electrode system made of LDPE(Low Density Polyethylene), observed inception and propagation of electrical tree by optical microscope and investigated the characteristics of the partial discharge (PD) pulses accompanying with propagation of electrical tree. In the specimens with needle-shaped void, the tree propagates branch type. The length of the tree has good linear relation with average discharge power of PD pulses. In the specimens without needle-shaped void, the tree grows bush type tree. The correlation between the area of the tree and the average discharge power of PD pulses has linear relation.

당뇨병유발백서에서 급성패혈증 병발시 적혈구막지질과산화의 변화

박성우,홍성관,유형준,장대영,강승식,유재명,임성희,최문기,노정우,이규만 대한당뇨병학회 1994 Diabetes and Metabolism Journal Vol.18 No.3

Semi - continuous Culture 방법을 이용한 Condensed Tannin 의 한국재래산양 반추위 섬유소 분해 미생물의 활성에 미치는 영향

배귀석,이상석,최종원,박상엽,장문백,하종규,최일,배희동,김종민 한국낙농학회 1999 韓國酪農學會誌 Vol.21 No.2

Zn-0.3wt.% Al 합금의 초소성 변형에 따른 미세조직의 변화

이원절,박찬경,하태권,손중락,장영원 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.9

The superplastic deformation of Zn-0.3wt.%Al alloys were investigated at room temperature under various strain rate. These alloys were highly elongated up to 1400% at the initial strain rate of 2×10^(-4)/s, revealing the rate sensitivity parameter of about 0.4. In order to investigate the microstructural change during superplastic deformation, the transmission electron microscopy(TEM) studies were performed on the specimen elongated up to the 100% tensile strain at various strain rate. The microstructure was composed of zinc rich matrix phase, with 1㎛ in grain size, and Al rich second phases precipitated generally at grain boundaries and/or triple point. In region III(5×10^(-2)/s), the high density of dislocations were observed within the grains and deformation twins were also formed within the grains. In region II(2^*10^(-4)/s), however, the dislocations were highly localized along the grain boundaries and deformation twins were not observed. Observation of severe deformation along the grain boundaries and grain boundary migration(GBM) suggest that grain boundary sliding(GBS) is a dominant mechanism of superplastic deformation in this alloy.

HVOF 용사법으로 제조된 TiC-Fe 합금 코팅층의 내마모 특성에 미치는 열처리 영향

김문철,박찬경,진현우,김현민,최상준,권순주 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.1

The physical soundness, microhardness and wear properties of the thermally sprayed TiC-Fe wear-resistant coatings have been investigated. Thermally sprayed coatings were fabricated by HVOF and the subsequent heat-treatments were carried out at temperatures ranging from 800℃ to 1000℃ in either vacuum or air for 30 minutes. The wear resistance of the as-sprayed TiC-Fe alloy coatings was found to be better than that of Cr₃C₂-NiCr alloy coatings and similar to that of WC-Co coatings. In addition, the wear resistance and hardness of the coating were improved by the following heat-treatment in vacuum(∼10^(-3)torr). The maximum improvement in wear resistance and microhardness was about 20 and 30%, respectively by the heat-treatment performed at 900℃ in vacuum, while the heat-treatment in air deteriorated the wear property due to oxidation. It has been revealed, from TEM and Mo¨ssbauer studies, that the improved wear resistance in the heat treated coating was mainly caused by the hardness increase associated with martensitic transformation. However, no improvement in the wear resistance of the TiC-Fe coatings heat-treated in air seemed to be caused by the residual stress due to the oxidation of Fe matrix.